Thymus exports precursors of innate lymphoid cells to the blood and peripheral tissues

Thymus has been shown to have a high capacity to support the differentiation of ILCs. Whether it actually contributes to ILC pools in the body is not clear. Single cell RNA sequencing analyses using wild type and athymic nude mice show a substantial amount of thymus-derived ILC precursors in the blood, along with differentiated ILC subsets which may or may not be generated in the thymus. The precursors express CD3 intracellularly (ic) but not on the surface. icCD3e+ cells are primarily found in immature forms in peripheral tissues including the lung, small intestine and epidermis, and differentiate into ILC subsets in different tissue environments in steady state. Helminth infection promotes their differentiation towards functional ILC2s. Thus, the thymus exhibits a previously unappreciated role in replenishing ILC pools in different peripheral tissues through life. This finding is of great significance in understanding age-related differences in immune responses and pathophysiology. Overall design: transcriptional profiling of ILC2 from WT, Nude, dKO, ID1 strains performed by single-cell RNA sequencing